Joseph L. Druce, charged with murdering defrocked priest John J. Geoghan, was severely beaten by his father as a child and was sexually abused, beginning at age 8, by three other adult men, including a neighbor and a man with a religious affiliation, according to an investigator hired by Druce's lawyer.

"His problems stem from his abuse as a child," Joseph Guidetti, the investigator, said of Druce. "He didn't have a chance in life from Jump Street."

Guidetti declined to release the names of the three men he said sexually abused Druce, saying the three -- who were not family members -- will be key witnesses for the defense when Druce goes on trial.

John H. LaChance, Druce's lawyer, has said he is investigating an insanity defense. Guidetti said that for such a defense, the alleged abusers are needed to corroborate Druce's assertions that he was sexually abused as a child.

Druce's father, Dana Smiledge, declined to comment yesterday at his home in Byfield.

Authorities said Joseph Druce, 38, beat and strangled Geoghan on Aug. 23 at the Souza-Baranowski Correctional Center in Shirley. Druce was serving a life sentence without possibility of parole for the 1987 murder of George Rollo, 51, of Gloucester, who Druce contended made a sexual advance after picking up Druce, who was hitchhiking.

In a court appearance Friday and in a Sept. 5 letter to the Catholic Free Press newspaper of the Worcester Archdiocese, Druce called on the public and lawmakers to step up protection of children and to "hold pedophiles accountable for their actions."

Guidetti said that when Druce was teenager, he told therapists about the sexual abuse he suffered, and that records now being reviewed will bear that out.

The investigator said he was in the process of contacting the three men who allegedly abused Druce. One of them lured Druce into his home in Druce's childhood neighborhood, Guidetti said. As a child, Druce lived in Danvers and Salem, Guidetti said, who added that he did not know without consulting his notes in which community the alleged abuse occurred.

Guidetti said Druce learned as a child that the man who sexually abused him had also sexually abused one of his friends.

Druce also was sexually abused by a man who had an affiliation with the church Druce's family attended, Guidetti said. However, that man was not a priest. Guidetti said he did not know without reviewing notes the church affiliation of the Druce family and the alleged abuser, but said the man had a supervisory role at the church.

Guidetti declined to provide any details about alleged sexual abuse by the third man. He described the three episodes of abuse as varying in duration when Druce was between ages 8 and 12. The three men were not connected, Guidetti said, and the abuse incidents were separate and independent.

Dana Smiledge, Druce's father, told the Boston Herald on Aug. 23, the day of Geoghan's murder, that his son had been a longtime victim of sexual abuse by adult men.

Last week, after Druce was arraigned on murder charges in Worcester Superior Court, his lawyer told reporters that Druce wanted to send a message to his father. Quoting his client, LaChance said: "If you knew about my being sexually molested, why didn't you do anything to protect me?"

LaChance did not return a call to his office yesterday.

In 1988, Druce's lawyers unsuccessfully attempted an insanity defense in the murder of Rollo. There was no evidence presented at that trial of Druce as a victim of sexual abuse, but there was testimony that Druce was prescribed pyschoactive pharmaceuticals since the time he was 5 or 6 until his middle teens.

Globe correspondent John McElhenny contributed to his report.Sean P. Murphy can be reached at smurphy@globe.com.